March 20 (Reuters) - Geron Corp said the U.S. Food and Drug Administration ordered a halt to new patient enrollments in an early-stage trial of its blood cancer drug, imetelstat, over concerns about liver damage.

The halt announced on Thursday was for enrollments in a trial sponsored by Mayo Clinic, and comes a week after the FDA ordered Geron to cease company-sponsored trials of the drug over similar concerns.

Imetelstat is Geron's only remaining drug and was touted as the company's savior after curing 22 percent of myelofibrosis patients in a trial last year.

Geron said on Thursday that it could not enroll new patients in the Mayo Clinic-sponsored study, but that the trial could continue with patients benefiting from the drug.

The FDA on March 12 had ordered a complete halt to trials that were testing imetelstat to treat thrombocythemia and multiple myeloma, two forms of blood cancer.

The Mayo Clinic had ceased enrollments in January and said that about 20 of 79 patients enrolled had dropped out.

The company's shares were down slightly at $2.27 in premarket trade on Thursday.

The stock lost 62 percent of its value on March 12 when the FDA halted the company trials. Since then the stock has risen 35 percent and closed at $2.28 on Wednesday on the Nasdaq.

(Reporting By Vrinda Manocha in Bangalore; Editing by Savio D'Souza)